1. Field of the Invention
The present invention relates to a power unit for driving a driven unit such as wheels of a vehicle.
2. Description of the Related Art
For example, as a vehicle, which runs by transmitting engine power to driving wheels as a driven unit, there has conventionally been known a vehicle which automatically stops engine operation during a stop at an intersection (so-called an idle-stop vehicle) as described in Japanese Patent Application Laid-Open No. 2003-269212 (hereinafter, referred to as Patent Document 1).
On the other hand, a vehicle generally includes various auxiliary devices such as a water pump, an air conditioner compressor, and a power steering pump. In this case, these auxiliary devices are able to be driven by using the engine power during engine operation. During the stop of engine operation, however, the auxiliary devices are not able to be driven by the engine.
Therefore, in the case of the idle stop vehicle as described in Patent Document 1, there is known a vehicle which has an auxiliary device driving motor to drive auxiliary devices by using the motor during the stop of engine operation as described in Patent Document 1.
Incidentally, the technique of driving the auxiliary devices by using the auxiliary device driving motor during an idle stop of the engine as described in Patent Document 1 is also applicable to a hybrid vehicle having an engine and a drive motor as power generation sources for driving the driving wheels of the vehicle.
In cases where the technique described in Patent Document 1 is applied to the hybrid vehicle, however, the auxiliary device driving motor is mounted on the vehicle in addition to the engine and the drive motor. Therefore, the technique has a problem of inhibiting a reduction in weight or downsizing and a decrease in manufacturing cost of the vehicle.